JPH04240384A - Plywood drying machine - Google Patents

Abstract

PURPOSE: To restrict the bent deformation of veneers, by arranging a plurality of rod-shaped electrodes along a veneer running path comprising a series of conveyor rollers in a dryer housing to radiate a radio frequency while circulating hot air onto both sides of the veneers. CONSTITUTION: A veneer running path comprising powered rollers (22a-22c) is provided in an elongated dryer housing 10, and the rollers 22 are rotated by a common drive chain 26. A pressure roller 38 is arranged parallel with and above the rollers 22 and an aluminum surface 32 is formed on the outer circumference of the rollers 22 and 28 to prevent fouling of veneers 24. Moreover, rod-shaped electrode pairs 50 and 52 and 60 and 62 are arranged between pairs of adjacent rollers, and a radio frequency is radiated from individual radio frequency energy generators to perform an induction heating of the veneers 24. The stream of hot air generated by a gas burner is circulated onto both sides of the veneers 24 through ducts 110 and 112.

Description

[Detailed description of the invention]

0001

TECHNICAL FIELD The present invention relates to a plywood dryer, and more particularly to a plywood dryer, and more particularly to a plywood dryer that uses radio frequency air in conjunction with medium-temperature circulating air to obtain sustained, uniform drying results with shorter drying times than prior art dryers. This relates to a plywood dryer that uses energy.

0002

BACKGROUND OF THE INVENTION Presently known plywood dryers typically rely on circulating hot air to perform the drying action of removing moisture from the wood.

0003

There are some problems when using these conventional dryers. For example, to perform adequate drying, many dryers require a large amount of floor space, which is undesirable. The high temperature of the air causes the wood to burn. Volatiles released at high temperatures are also a problem. The drying results are not uniform and are highly dependent on the type and texture of the wood being treated and its moisture content.

0004

[Means for Solving the Problems] The present invention provides excellent drying results by using radio frequency energy to release moisture contained inside the wood to the surface of the wood in a continuous plywood dryer. It is based on the discovery that Moisture on the surface is evaporated and removed by a stream of air heated to medium temperatures. For example, 250 to 350°F
It has been discovered that temperatures within the range of . As a result of the use of radio frequency energy, drying results are much less dependent on wood type, texture and initial moisture conditions. Only medium-temperature air is used, eliminating the tendency for wood to scorch. There is also no problem of overdrying, and organic substances released at high temperatures are avoided. Due to the increased dryer efficiency, much less dryer floor space is required for a given amount of veneer than a conventional dryer. It is therefore an object of the present invention to use radio frequency energy to release the internal moisture of the veneer and direct it to the surface of the veneer;
The object of the present invention is to provide a continuous plywood dryer in which drying is facilitated by a circulating flow of medium-temperature air. Another object of the invention is to provide a dryer that includes a conveyor roller with an aluminum surface layer and a pressure roller for transferring veneer sheets through the dryer. Due to the use of the aluminum layer, staining of the treated wood is minimized. Through the use of pressure rollers, the veneer is effectively subjected to an ironing action. Upon drying, bending and deformation of the plywood is reduced. Yet another object of the invention is that the radio frequency energy electrodes used to apply radio frequency energy to the veneer are continuous in the form of aluminum electrodes distributed longitudinally of the dryer and interposed between the conveyor rollers. We offer a variety of plywood dryers.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to FIGS. 1 to 4. The dryer illustrated in the accompanying figures includes an elongated drying housing 10. The veneer board enters the drying housing while running between the pair of rollers 14,16. The veneer board runs between the pair of rollers 18, 20 as it exits the drying housing.

The plywood running through the housing is carried on powered rollers 22, 22A, 22B and 22C. These drive rollers extend transversely to the housing and are generally parallel to the rollers 14, 16, etc. which carry the plywood into the housing. These rollers 22 are laterally spaced from each other and their upper surfaces are disposed in a generally horizontal plane, forming a running path for a plywood board 24 within the housing. These rollers are driven by a drive chain 26 as shown in FIG. This chain 26 runs over a sprocket 28 connected to the rollers for rotation therewith, and over an additional idler sprocket 30. Chain drive is performed by a conventional motor (not shown).

The conveyor roller has an aluminum surface 32. This aluminum surface has been found to be effective as it prevents the tendency of the veneer to be contaminated as it runs through the dryer. To form the aluminum surface of the conveyor roller (and the pressure roller described below), the roller is manufactured such that the outer surface of the aluminum tube segment forms the outer circumferential surface of the roller. A support shaft extends along the axial direction of the aluminum tube, and a sleeve of dielectric material distributed along the length of the support shaft is interposed between the tube and the shaft to support the tube. In a structure in which the tube and the shaft are rotated as a unit, the tube and the shaft are interconnected, and the tube rotates as the shaft rotates. In an idler type structure, the dielectric material rotatably supports the tube on the shaft, and the tube and shaft rotate relative to each other.

In this dryer, a suitable mounting member for the conveyor roller shaft 34 is provided to mount the roller shaft on the conventional frame of the dryer. It has been discovered that certain types of wood veneers bend or otherwise deform from their generally flat condition as a result of the thermal drying action that occurs during dryer operation. To prevent this deformation, an ironing mechanism is provided to apply a continuous flattening action to the veneer as it travels through the dryer.

More specifically, a pressure roller 38 is disposed above and parallel to each conveyor roller. These rollers 38 also have an aluminum surface. This aluminum surface has an axis 40 extending through the center of the roller.
It is rotatable relative to the Both ends of the shaft 30 are supported within blocks 42, each block being mounted to slide up and down between a pair of opposing tracks 44,46. In the above structure, gravity acts to cause each pressure roller to flex downwardly into contact with the conveyor roller. The veneer passes through a nip between a respective pressure roller and a conveyor roller and is flattened or ironed as it passes. In the dryer of the present invention, elongated rod-shaped electrodes parallel to each other and parallel to the axes of the conveyor roller and pressure roller are arranged between adjacent pairs of rollers, and each electrode pair extends along the longitudinal direction of the dryer. arranged alternately with roller pairs. An example of such an electrode is electrode pair 5 disposed between conveyor roller pair 22A and 22B.
0, 52 and a pair of electrodes 60, 62 disposed between the pair of conveyor rollers 22B, 22C.

The plywood traveling through the dryer passes through the spaces between each electrode of each electrode pair. These electrodes are shown in Figure 4.
receive radio frequency energy, such as using the system shown in the figure. More specifically, a radio frequency energy generator 70 is provided. The generator includes a pair of terminals 74, 76 which receive energy of opposite polarity sign during operation of the generator. The electrodes of each electrode pair are interconnected. R. F. A pair of electrodes connected to one terminal of the generator is connected to this R. F. They are arranged alternately with respect to the electrode pairs connected to the other terminal of the generator. Thus, the radio frequency energy generator is connected through successive pairs of electrodes extending through the plywood.

Radio frequency energy generators can operate with any frequency commonly used for dielectric heating. For example, frequencies between 3 MHz and 27 MHz have been used. A stream of moderately heated air that can travel along the surfaces of the plywood and remove moisture trapped on these surfaces, together with the radio frequency energy, dries the plywood.

More specifically, the natural gas burner 100,
When an air heater such as 102 is activated, it produces a hot air flow that travels down through the ducts 106 , 108 . These ducts connect to hot air ducts 110, 112 that extend longitudinally inside the dryer (FIG. 3). Hot air exits from these ducts through nozzles 114, 116 and is forced towards the surface of the plywood board running through the dryer.

Additionally, circulation fans 120, 122 circulate the hot air within the dryer. A quantity of air containing moisture is discharged from the dryer through a discharge duct 126 that connects with the interior of the dryer at a mutually spaced point. The movement of air through this exhaust duct 126 is controlled by an exhaust fan 130.
caused by the action of The plywood processed in a typical dryer and its operation generally has a thickness of 1/10 inch and a width of 4 to 5 feet transverse to the plywood run. 3-3/4 inch diameter conveyor rollers and pressure rollers can be used. The temperature of the hot air for removing moisture from the plywood surface can range from 250 to 350 degrees Fahrenheit.

[0014]

The application of radio frequency energy to the plywood helps to force moisture retained within the plywood to the surface of the plywood. As moisture collects on the veneer surface, the hot air flow evaporates this moisture and the exhausted air removes this moisture from the drying chamber. If the dryer of the present invention is used, the drying time required to achieve a predetermined moisture state in the plywood will be 1/2 to 1/3 that of a conventional dryer. Of course, this means that for a given degree of dryness the space required is reduced. A veneer board with a more uniform moisture content is produced. Also, heat loss due to high temperature use is reduced. The present invention is not limited to the above description, and can be modified or implemented as desired within the scope of the spirit thereof.

[Brief explanation of the drawing]

FIG. 1 is a schematic partial side view of a dryer according to the invention.

FIG. 2 is a schematic partial plan view of a dryer according to the invention.

FIG. 3 is an enlarged sectional view of a part of the dryer according to the invention.

FIG. 4 is a circuit diagram showing the connections of a radio frequency energy generator used in the dryer of the present invention.

[Explanation of symbols]

10 Dryer housing 22 Drive roller 24 Plywood board 26 Drive chain 32 Aluminum layer 38 Pressure rollers 50, 52, 60, 62 Electrodes 70 Radio frequency energy generator 100, 102
Gas burner 114 Hot air nozzle 130 Exhaust fan

Claims (8)

[Claims] 1. A dryer housing, a series of conveyor rollers mounted at regular intervals in the housing to define a plywood run through the dryer, and a series of conveyor rollers mounted in the housing at regular intervals to define a plywood run through the dryer. a radio frequency energy generator comprising a plurality of rod-shaped electrodes arranged in a row, a radio frequency energy generator connected through the electrodes, and means for circulating hot air against both sides of the plywood sheet conveyed by the conveyor rollers. Continuous plywood dryer used. 2. A pressure roller is disposed parallel to and above each of the selected conveyor rollers, and the pressure roller is deflected relative to the conveyor roller below. The dryer according to item 1. 3. The dryer according to claim 1, wherein said air circulation means includes a plurality of nozzles that direct hot air against the surface of the plywood. 4. The dryer of claim 2, wherein the conveyor roller and the pressure roller have aluminum outer surfaces and include non-conductive means for mounting the rollers within the dryer housing. Machine. 5. A drying housing, a series of conveyor rollers mounted at regular intervals in the housing and defining a run of plywood through the dryer, each of the conveyor rollers alternating with the conveyor rollers along the length of the dryer. , a frequency generator having a plurality of rod-shaped electrode sets including upper and lower electrodes disposed on both sides of the plywood track, a pair of terminals receiving energy of opposite polarity sign, and one terminal of the pair of terminals. is connected to a part of the electrode pair, the other terminal is connected to another of the electrode pairs, and the electrode pairs connected to the one terminal are arranged alternately with the electrode pairs connected to the other terminal. and conductor means extending in the direction of travel of the plywood through the dryer. 6. Pressure rollers are disposed above each of the selected conveyor rollers in parallel and opposed to each other, and these pressure rollers are deflected relative to the conveyor rollers below. The dryer according to claim 5. 7. The dryer of claim 6, wherein the conveyor roller and pressure roller have aluminum exterior surfaces and include non-conductive means for mounting the rollers within the dryer housing. Dryer. 8. The dryer of claim 7, wherein said air circulation means includes a plurality of nozzles directing hot air against the surface of the plywood sheet as it travels through the dryer housing.